In recent years, the demand for high performance batteries has increased, driven in part by the increasingly large number of portable consumer electronics products and growing needs of batteries for fuel efficient vehicles. Lithium-ion batteries are found in many applications requiring high energy and high power densities, as they can provide high volumetric and gravimetric efficiency in battery packs for use in portable electronic devices and in fuel-saving vehicles.
Lithium-ion cells require tabs for making the connections between their internal active material and external power terminals. The tabs are typically attached directly to the current collectors. Coupling between the tabs and the electrodes can be difficult especially for cells having graphite sheet current collectors. One reason involves differences in the physical properties of the tabs and the current collectors. This dissimilarity in material properties can lead to high contact impedance, brittle joints or other unacceptable performance-related problems. To address such problems, current coupling methods have involved ultrasonic welding and resistance spot welding to achieve a secure joint between the tab and pin. Unfortunately, these methods are not suitable for attaching a metallic tab to a graphite based current collector.
Therefore, there is a need to develop other tabbing methods for attaching tabs to electrochemical cells, such as lithium-ion cells having carbon sheet current collectors. The present invention satisfies these and other needs.